Why is Minnesota cutting out so much of the math that California and Texas teaching? The students often end up going to the same colleges, where they will need to do the same work?
It almost certainly isn't just that MN is a simple subset of the CA/TX material, or else the Byron district's scores wouldn't have gone up from the new material.
End result: we learned the same material, just in a different order.
Secondly, different teachers have different experiences and teach differently. We're human!
How could it be the same? The only way I see is to remove as many human elements as possible (teachers most notably). Are we headed that way?
States are the ones responsible for picking what material to teach their children. This is why material can be different.
There is so much that we could teach our children, there isn't a clearly defined set of "This is what is best to teach them", so different people will produce different sets of things to teach. This is why material is different.